The advent of light-weight,
flexible or curved displays for consumer products requires the introduction of
reliable film lift-off processes into large scale production. Laser Lift-Off
(LLO) or UV Laser Peeling (ULP) with solid-state UV lasers and optical systems
VOLCANO UV from INNOVAVENT open the door to reliable and cost-effective
Laser Lift-Off processes have been investigated since more than a decade. A typical example of industrial applications can be found in the LED industry for separating light-emitting films like GaN from sapphire substrates where they are grown by vapor deposition processes.
With the growing interest in high-performance consumer goods like smartphones, e-books, smart watches and TV sets with resolution beyond HD and 3D capability it also became of interest to produce dis-plays which are no longer flat. They are curved as for giant TV screens and mobile devices or they are flexible as for e-book readers. In all these cases the producing companies face the challenge to manufacture displays on flexible or free-form substrates. With the present production tools which are designed for flat panel manufacturing up to Gen 8 substrates (2500mm x 2200mm) it is not feasible to make free-form or flexible devices.
The way out is offered by laser lift-off processes. The basic idea behind this production scheme is to manufacture a functional display film on a rigid substrate like a flat glass panel and subsequently attach a flexible substrate to the film. Then the film with the flexible substrate has to be separated from the glass panel. The technology of choice for this separation process is laser lift-off, as it allows to process large area devices with the required gentleness and reproducibility. The 343nm and 355nm laser light transfers through the glass with no attenuation and is absorbed in the functional film or in a sacrifice layer. The pulsed laser energy results in the delamination of the film from the glass carrier.
VOLCANO UV Laser Optics generates a laser line of 100mm to 750mm length and a width of 20-30µm FWHM. The line is focused on the polyimide through the glass at energy density of 150-500mJ/cm² and scanned with a typical pitch 10-20µm. The TruMicro 7370 laser emits 15ns pulses at 10 kHz and delivers a very efficient and reliable procedure. When applying a sacrifice layer (50-60nm a-Si) between glass and polyimide higher energy density of 500mJ/cm2 is required.
Gaussian fit to the short axis profile of the laser line beam
Long axis profile over 250mm of the laser line, p2p<=5%